The present invention relates generally to analog-to-digital converters and, more particularly, to sigma-delta type analog-to-digital converters.
A majority of modern digital communication systems use complex (I and Q) modulation schemes and a large amount of signal processing (equalizer, adaptive filtering, FSK demodulation, etc.). Most of this signal processing is only possible in the digital domain and applies to complex signals (a complex signal is represented by two signals, one corresponding to the real part, the other to the imaginary, also called in phase I, and in quadrature Q). This implies the Analog to Digital conversion of the two analog signals I and Q. Those two signals are typically the output of two mixers mixing down the RF carrier with a local oscillator in phase and in quadrature. The I and Q channels have, by construction, the same dynamic range and bandwidth.
The converter presented herein, in accordance with at least one presently preferred embodiment of the present invention, can be used in any system requiring simultaneous conversion of several analog channels of equal dynamic range and is therefore well adapted to the Analog to Digital conversion needs of a modern digital radio receiver.
In summary, at least one embodiment of the present invention provides apparatus for providing analog to digital conversion, the apparatus comprising: an input having at least two channels; an output having at least two channels; a multiplexer associated with the input; a single low-pass filter associated with all of the at least two channels of the output; and at least one component which implements a delay prior to a signal reaching the low-pass filter.
Further, at least one embodiment of the present invention provides a method of providing analog to digital conversion, the method comprising the steps of: inputting a signal having at least two channels; outputting a signal having at least two channels; providing a multiplexer associated with the input; providing a single low-pass filter associated with all of the at least two channels of the output; passing a signal through the single lowpass filter; and implementing a delay prior to the signal reaching the low-pass filter.
Additionally, at least one embodiment of the present invention provides a program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform method steps for providing analog to digital conversion, the method comprising the steps of: inputting a signal having at least two channels; outputting a signal having at least two channels; providing a multiplexer associated with the input; providing a single low-pass filter associated with all of the at least two channels of the output; passing a signal through the single low-pass filter; and implementing a delay prior to the signal reaching the low-pass filter.
For a better understanding of the present invention, together with other and further features and advantages thereof, reference is made to the following description, taken in conjunction with the accompanying drawings, and the scope of the invention will be pointed out in the appended claims.